JPH0115770B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion control device designed to ensure stabilization time for a pilot flame in a combustion sequence.

Normally, in a combustion furnace with a relatively large capacity, when igniting a gas or liquid fuel, a predetermined control device passes through at least three operating periods: a pre-purge period, an ignition trial period, and a flame stabilization period. The engine is now in a normal combustion state. In particular, immediately after the ignition trial period has elapsed, the flame becomes unstable as the furnace is still cold, which tends to cause a lift phenomenon.Furthermore, with liquid fuel, the flame becomes unstable as the igniter stops operating. do. Second, from the point of view of the need to monitor a normal flame that is not caused by the igniter's spark in the single pilot flame state after the igniter stops operating, the combustion flame at startup is stabilized for a certain period of time.
It is then desirable to ignite the main fuel from the main fuel supply. For this reason, after an ignition trial is attempted, a so-called pilot only period or pilot flame stabilization period is added to the fuel sequence.

However, conventionally, the majority of methods to obtain this fuel sequence have been to use a mechanical timer mechanism that combines a cam and a synchronous motor. It was considered to be of low gender.

However, in recent years, fuel control equipment has also been required to be equipped with various additional functions, such as changing the combustion sequence or interlocking with supply air amount control equipment such as dampers. It is being changed to fuel sequence control. However, the problem here is that it is necessary to provide high reliability and fail-safe properties against conduction or open failure of circuit elements of the sequence circuit.

The present invention, in such a combustion sequence control device for an electronic circuit, prevents shortening of the flame stabilization period in response to a failure of an electronic circuit element, and also prevents shortening of the main fuel when the flame stabilization period expands. The object of the present invention is to provide a combustion control device in which the circuit itself can self-check to block the supply.

That is, the first relay controls the operation of the blower and the second fuel supply device during the pre-purge period from the generation of the heat request signal from the thermostat, and also controls the operation of the second fuel supply device during the normal combustion operation after the pilot flame stabilization period. The present invention is applied to a combustion control device having a load drive circuit that maintains the operation of the blower by a second relay that controls the operation of the first fuel supply device, and further receives the heat request signal and receives the first relay. a first thyristor connected in series with the relay, a fail-safe timer circuit that starts timing from the start or end of the ignition trial period and outputs a timing signal at the completion of the pilot flame stabilization period; The present invention provides a combustion control device that includes a semiconductor switching element for turning off a first thyristor, prevents shortening of a flame stabilization period, and ensures that main fuel is not ignited until a predetermined period has elapsed.

The combustion control device of the present invention can be applied to both gas combustors and liquid combustors, and can be applied to any combustion device that sequentially controls two combustion supply control devices, regardless of the shape and type of burner. Ba,
Applicable to any format.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a combustion control device according to a first embodiment of the present invention. In the figure, terminals L1 and L
An AC commercial voltage source 10 is connected to 2, and a voltage is applied between conductive wires 11 and 12. This AC voltage is applied to a load drive circuit 20 consisting of relay contacts of an electronic sequence circuit 30, and a combustion load circuit 1 consisting of a blower 13, first and second fuel suppliers 14 and 15, an igniter 16, and an alarm 17.
It supplies power to 9 and 9. Additionally, the alternating current voltage between conductors 11 and 12 is applied to an autotransformer 18 which connects directly to flame detection circuit 31 via conductors 23 and 25 and to thermostat 21 and diode rectifier circuit 22. Combustion sequence circuit 3 through
0 and a DC rectified voltage is applied to each. Although the flame detection circuit 31 can be an ultraviolet detection terminal or any other known detection circuit, a flame rod detection terminal 32 that utilizes flame rectification is exemplified here.

On the other hand, the combustion sequence control device 30
It begins with operation of the safety switch drive circuit 35, which is energized with a DC voltage between 4 and 25. This switch drive circuit 35 includes resistors 36, 37, 38
and 39, a series circuit of a transistor 40, a safety cutoff switch 41, and a semiconductor switching element, ie, an SCR 42, and a series circuit of a transistor 45 and resistors 46 and 47, each of which has a DC current. It is connected in parallel to the power supply 22. Further, the base 43 of the transistor 40 is connected to the connection point of the resistors 36 and 37, and
7, a series circuit of a transistor 45 and a second relay normally open contact 2K2 is provided;
Furthermore, the emitter of transistor 45 is SCR42
A feature of this drive circuit 35 is that it is connected to the gate 44 of the drive circuit 35 via a resistor 46, so that even if any of the circuit elements constituting this drive circuit 35 has a short or open failure, Consideration is given to either operating the safety switch 41 or preventing the combustion sequence from proceeding.

Furthermore, a wind pressure switch 49 is connected to one end of the safety switch 41, and its normally closed contact and resistor 5
3 and 54, and the first relay normally closed contact 13
A blower and fuel control circuit 50 that controls a fan and a second fuel supply device (e.g., main valve) including a semiconductor switching element, that is, an SCR 51 and a first relay 52 (or 1K), to which a heat request activation signal is input via a heat request activation signal is connected. has been done. Further, a normally open contact of the wind pressure switch 49 is connected to an electronic timer circuit 60 via a second relay 61 (or 2K). The second relay 61 controls the first fuel supply device 14 .

The electronic timer circuit 60 is, for example, disclosed in Japanese Patent No.
A known timer circuit disclosed in the specification of No. 972842, which includes a voltage divider circuit of resistors 55 and 56;
a time constant circuit of a resistor 57 and a capacitor 58;
Two semiconductor switching elements, namely PUT6
2 and the SCR 42 described above. This timer circuit 60 is also as described in the same Japanese patent.
The second relay 61 and output transistor 64
is formed so as not to give false signals to the

On the other hand, the output of this electronic timer circuit 60 gives a signal to the output transistor 64, and as the transistor 64 operates, it controls the third relay 78 (or 3K) that energizes the igniter 16, and at the same time controls the third relay 78 (or 3K) that energizes the igniter 16. It is giving an input signal.

Finally, as the most important feature of the invention, a fail-safe second timer circuit 65 and its output transistor 71 are connected to the blower and fuel control circuit 50 to ensure a flame stabilization period.
This second timer circuit 65 includes a time constant circuit consisting of a resistor 66 and a capacitor 67 that are charged from the conductor 24 through the transistor 45, a voltage dividing circuit consisting of two resistors 68 and 69, and a semiconductor switching element, ie, a PUT 70. configured.
Further, the cathode of this PUT70 is connected to the base of the output transistor 71, and the collector-emitter of this transistor 71 is connected as described above.
The anode and cathode of SCR51 are connected in parallel. Like the first timer circuit 60, the second timer circuit 65 functions as a type of fail-safe one-shot circuit, and supplies a pulse-like output to the transistor 71 after a certain period of time, but does not repeat the oscillation operation thereafter. .

Next, the combustion sequence operation of the embodiment shown in FIG. 1 will be explained with reference to the sequence diagram shown in FIG. 2a. First, we will discuss the normal combustion sequence. thermostat 2
1 is turned on and a voltage is applied between conductive wires 24 and 25, and at the same time, current is applied through resistors 36, 37, 38 and 39, and transistor 40 becomes conductive. At this time, if the wind pressure switch 49 is normally connected to the normally closed contact side, the transistor 40, the safety switch 41, the resistor 53, and the normally closed contact 13 are connected.
The gate of SCR51 is activated. So SCR5
1 turns on and energizes the first relay 52, and the blower 13 starts to start via the normally open contact 1K1 of the load drive circuit 20, and its respective contacts 1K2, 12,
1K3 and 13 are reversed. When it is confirmed that the control circuit 50 operates normally by reversing the contacts 1K3 and 13, and that the air blowing operation normally occurs by reversing the wind pressure switch 49, the electronic timer circuit 60 detects the wind pressure for the first time. Voltage is supplied from the normally open contact of the switch 49 to the voltage divider circuit via the diode 54, and to the time constant circuit via the relay normally open contact 1K3. This timer circuit 60
The charging time of the capacitor 58 when the PUT 62 is not conductive is selected as the pre-purge period, and the discharging time after the PUT 62 is conductive is selected as the ignition trial period.

When a predetermined time, that is, a pre-purge period has elapsed due to the voltage comparison operation between the anode and base of the PUT element 62, the PUT 62 becomes conductive, and discharge of the capacitor 58 is started, and this discharge current flows through the resistor 59 to the transistor 64. is conducted,
Subsequently, the third relay 78 is further energized and the transistor 45 is also turned on. As the transistor 45 becomes conductive, the SCR 42 is triggered through the resistor 46 and becomes conductive, and the time constant circuit of the second timer circuit 65 starts charging. When SCR42 turns on,
Normally open contact of wind pressure switch 49 and second relay 6
1, the voltage applied between the anode and cathode of the diode 63 is reversed and the cathode potential thereof drops, so that the charge in the capacitor 58 is discharged with a larger current through the second relay 61 than through the resistor 59. Therefore, the second relay 61
energized by this discharge current flowing through 42,
All the contacts 2K1, 11, 2K2, 2K3 are reversed, the first fuel supply device 14 is energized, and the contact 2
A self-holding circuit is formed through K2 and the conductor 48 to the second relay 61 while the transistor 45 is ON, and at the same time, the resistors 36 and 37 are short-circuited, so the transistor 40 is OFF.
As a result, the operation of the safety switch 41 is prevented.

On the other hand, since the third relay 78 is also energized, the contacts 3K1 and 31 are reversed, so the load drive circuit 20
At the same time, the igniter 16 is also energized and an ignition trial period begins, which continues in this sequence until the discharge of the capacitor 58 is completed.

Now, if a flame is not established within this trial period, the base input to the transistor 64 disappears as the discharge of the capacitor 58 ends, and the transistor 64 turns OFF.
Therefore, the transistor 45 is also turned off, the self-holding of the second relay 61 is released, and the relay 61 is turned off.
At the same time, the transistor 40 turns on, so the safety switch 41 operates via the SCR 42, which is already in a conductive state, and its contacts SS-1 and SS
-2 are each reversed to cut off all circuit operations, activate the alarm 17, and return to the original state, but are not recycled. Safety cutoff switch 41
can be any normal manual return type,
Further, it may be of an instantaneous action type or a delayed action type.

Further, if a flame is established during the trial period, the detection end 32 and the detection circuit 31 sense this, and the output transistor 33 becomes conductive, energizing the transistor 45 via the resistor 77. For this reason,
Even if the transistor 64 is turned off after the capacitor 58 has finished discharging, the third relay 78 is deenergized, and the igniter 16 stops operating, the transistor 45 continues to conduct, thereby controlling the energization of the first fuel valve 14. The operation of the second relay 61 continues to maintain self-retention. As a result, during the period T3, the first valve 14
A so-called pilot-only period or flame stabilization period progresses in which only the flame is operated.

On the other hand, the second timer circuit 65
Charging of the capacitor 67 is started simultaneously with the conduction of the PUT 5, and a comparison operation is performed between the predetermined gate voltage of the PUT 70, which has already been applied, and the anode side charging voltage. That is, these two voltages are the sum of the above-mentioned trial period T2 and flame stabilization period T3 (T
2+T3), the PUT70 turns ON after the period T3, and the discharge current of the capacitor 67 increases to that PUT70.
It flows in a pulsed manner through the resistor and the base-emitter of transistor 71.

As a result, the output transistor 71 becomes conductive, and a parallel conduction circuit between the SCR 51 and the transistor 71 is temporarily formed. However, in reality, the internal impedance of the transistor 71 is lower than that of the SCR 51, and the holding voltage of the SCR 51 is cannot be maintained, so the connection between the anode and cathode of the SCR 51 is cut off and turned OFF. However, since the base input to the transistor 71 is in the form of a pulse, the transistor 71 is also turned off immediately. Therefore, the first relay 52 is also deenergized, and all its contacts are reversed, causing the load drive circuit 2
0, the second fuel supply device, that is, the second valve 15 is opened, ignition is performed from the first valve 14, and normal combustion continues until the heat request signal from the thermostat 21 disappears as shown in FIG.

Next, another embodiment of the combustion control device of the present invention will be described with reference to FIG. The control device shown in FIG. 3 is an improved version of the control device shown in FIG. 1 only in the combustion sequence circuit 30, and the other parts are the same. Furthermore, since most of the combustion sequence circuit shown in FIG. 3 is similar to the circuit configuration shown in FIG. 1, only the different parts will be explained. The first difference is that the output transistor 71 has an SCR5 between its collector and emitter.
1, the base and emitter are connected via a diode 81, and secondly, a damper 110, a damper energizing circuit 111, and a fourth relay contact 4K1 are added, and the anode of the SCR 51 and the cathode of the PUT 62 are connected. The damper control circuit 80 is connected to the conductors 24 and 2, respectively.
5 and further includes a high or low interlock switch 100 or 101 that indicates the open or closed state of the damper, and thirdly, a third relay 78 that controls the igniter 16.
(or 3K) via the transistor 79, and the time constant circuit of the second timer circuit 65 is controlled by the transistor 79.

In other words, in the circuit shown in Fig. 1, there is no linkage with the control device for the amount of air supplied to the furnace, and since the transistor 71 and the SCR 51 are installed in parallel, if there is a conduction failure in either one, the ignition trial operation will not proceed. Although the first valve 14 and the igniter 16 perform the ignition operation, there is a drawback that the second valve 15 does not operate. This will lead to a decrease in the heat capacity of the boiler, etc., so the operator will know that the control equipment has failed at that point and there is no particular danger of releasing unburned fuel, but it is desirable to prevent the ignition trial operation from proceeding in this case as well. It's better to.

In the combustion sequence circuit 30 of FIG. 2, the connection point of the output transistor 71 is changed as shown, and the interlock switches 100 and 101 are used in the damper control circuit 80 to control the output of the transistor 71 and the SCR 51. Provides a solution to continuity faults. That is, the damper control circuit 80 controls the fourth relay 86 (or
K) has a transistor 87 connected in series with
Furthermore, a conducting wire 90 is provided to control the base input of this transistor 87, a pair of transistors 88 and 89 controlled by the output of PUT 62, and resistors 91 and 9 for biasing these transistors.
2, 93, 94 and 95.

The normal combustion sequence controlled by the three output relays 52, 61 and 78 in the embodiment of FIG. 3 is almost the same as the operation sequence shown in FIG. 2a, but the damper operation sequence shown in FIG. 2
It is controlled in accordance with each timing shown in Figure a. That is, when there is a heat request from the thermostat 21, the transistor 87 becomes conductive through the resistors 91, 92, 93, and 95, and the damper 110 is connected to the damper motor 112 through the fourth relay 86 and its contact 4K1.
Developed by. When this opening operation is completed, the high interlock switch 100 is closed by a known mechanism, and charging of the first timer 60 is started.
After that, when the PUT 62 is turned on, not only the transistor 64 is connected from its cathode through the resistor 59.
A pulsed input signal is input to the transistor 88 via the diode 84 and the capacitor 85,
When it becomes conductive, the transistor 89 also becomes conductive.
Even after the pulse input disappears, the conduction state is maintained by the action of both transistors 88 and 89. As a result, the transistor 87 is turned off as the input voltage drops,
The fourth relay 86 is also deenergized and the damper 110 is closed.
When this closing operation is completed, the transistor 64 is turned on by the operation of the low interlock switch 101.
Turn ON and perform the ignition trial operation described in Figure 1. Further, after the flame stabilization period T3 has elapsed due to the action of the second timer circuit 65 and the transistor 71,
The SCR 51 is turned off and the first relay 52 is deenergized,
The second fuel supply device 15 is ignited. At this time, at the same time
Since the anode potential of SCR51 increases, the conductor 9
The base of transistor 87 is again biased from zero through resistors 94 and 95 and turned on. Therefore, the damper opens again and normal combustion begins.
Next, consider conduction or open failure of circuit elements.

(i) In case of conduction failure of transistor 71; SCR
51 is never triggered, it does not start from the moment the thermostat 21 is turned on.

(ii) In case of open failure of transistor 71; SCR
51 is not turned off and the second valve 15 does not operate, it is possible to recognize the lack of heat capacity.

(iii) In the case of a conduction failure of the SCR 51; due to the drop in the anode potential of the SCR 51, the base input voltage of the transistor 87 decreases and cannot be turned on, and the high interlock switch 100 cannot be turned on, so the pre-purge operation cannot be performed.

(iv) In the case of SCR51 release failure; the first relay does not operate, so the pre-purge operation does not start.

Further, regarding the element failure of the second timer circuit 65, it is as follows.

(i) Resistor 68 failure; PUT to start charging when released
Although transistor 70 is turned on, the base input is suppressed by resistors 66 and 72 to a value at which transistor 71 is not turned on. PUT70 will not turn on in case of short circuit.

(ii) Failure of resistor 69: In this case, the relationship is opposite to that of resistor R1.

(iii) Resistor 66 failure; in release, PUT70 is ON
There is no short-circuit failure due to the use of wire-wound resistance.

(iv) Failure of capacitor 67; in release, PUT7
0 is not turned on, and in the case of a short circuit, the PUT 70 is turned on, but no pulse output is produced, and since the output voltage is suppressed by the resistor 72, the transistor 71 is not turned on.

(v) PUT 70 failure: Normal oscillation will not occur if there is an open or short circuit between the anode and gate, between the anode and cathode, or between the gate and cathode, and the base input will not function normally enough to turn on transistor 71. No pulse input is applied.

As described above, according to the present invention, in the combustion sequence operation, there is no danger that the flame stabilization period T3 provided at the beginning of ignition of the fuel will be short-circuited, and the unstable flame will cause the main fuel to Prevents fire from spreading.

[Brief explanation of drawings]

FIG. 1 is a circuit connection diagram of a combustion control device according to a first embodiment of the present invention, FIG. 2a is a combustion operation sequence diagram of the same control device, and FIG. A wiring diagram of a combustion sequence circuit that is a part of the combustion control device is shown, and FIG. 2b shows an operation sequence diagram of a damper control circuit provided in the combustion sequence circuit. 19... Combustion load, 20... Load drive circuit, 3
0... Combustion sequence circuit, 31... Flame detection circuit, 35... Safety switch control circuit, 50... Air blowing and fuel control circuit, 60... First timer circuit, 65... Second timer circuit, 52, 61 ,78
and 86... relay, 80... damper control circuit, 110... damper, 111... damper drive circuit.

Claims (1)

[Claims] 1. By the first relay that controls the operation of the blower and the second fuel supply device from the time when a heat request signal is generated from the thermostat during the pre-purge period, and after the pilot flame stabilization period has elapsed. The combustion control device maintains the operation of the blower by a second relay that controls the operation of the first fuel supply device during the combustion operation, and the combustion control device further receives the fuel request signal and is connected in series with the first relay. a first thyristor, a fail-safe timer circuit that starts timing from the start or end of the ignition trial period and outputs a timing signal at the completion of the pilot flame stabilization period; and a fail-safe timer circuit that receives the timing signal and turns off the first thyristor. and a semiconductor switching element for ensuring a flame stabilization period. 2. In claim 1, the timer circuit comprises a time constant circuit consisting of a resistor and a capacitor, and a second thyristor element, and outputs a pulsed timing signal to ensure flame stabilization time. Combustion control device. 3. In claim 2, the first thyristor is a silicon controlled rectifier (SCR), the semiconductor switching element is a transistor, and the collector and
A combustion control device that ensures flame stabilization time by connecting the emitters in parallel between the anode and cathode of the above SCR. 4. In claim 2, the first thyristor is a silicon controlled rectifier (SCR), and the semiconductor switching element is a transistor, and the collector of the transistor is
A combustion control device that secures flame stabilization time by connecting emitters in parallel between the base and cathode of the SCR, and adding a microvoltage element to the cathode of the SCR. 5. In claim 3 or 4, combustion control is provided to ensure flame stabilization time by applying the heat request signal to the gate of the SCR via the normally closed contact of the first relay. Device. 6 In claim 5, the above-mentioned
A combustion control device that ensures flame stabilization time by applying the heat request signal to the gate of the SCR through a series circuit of the normally closed contact of the first relay and the normally closed contact of the wind pressure switch. 7 In claim 6, the combustion control device further includes a second time constant circuit and a second PUT element that are charged via a normally open contact of the wind pressure switch and a normally open contact of the first relay. a second timer circuit including:
an output circuit that causes the second time constant circuit to select a charging time during the pre-purge period and a discharging time during the ignition trial period, respectively, and energizes the second relay when the second PUT element is conductive; A combustion control device for ensuring flame stabilization time, comprising a holding circuit that self-maintains the operation of the relay at least during the ignition trial period. 8 In claim 7, the self-holding circuit includes a second transistor to which the ignition trial operation signal from the second timer circuit and a flame signal from the flame detection circuit are input, and a normally open state of the second relay. A combustion control device that secures flame stabilization time by having a series circuit with a contact point. 9. In claim 8, the combustion control device further includes a third transistor and a safety cut-off switch from a power source via the thermostat;
a series circuit of a fourth semiconductor switch; a voltage dividing circuit comprising at least two resistors; a circuit connecting the voltage dividing circuit to the base of the third transistor; a safety cut-off switch drive circuit including a circuit for energizing a semiconductor switch, and further comprising: a flame stabilizing circuit, the voltage divider circuit being connected in parallel to the series circuit formed by the second transistor and the normally open contact of the second relay; Combustion control device to ensure time.